An apparatus is known, for the nondestructive ultrasonic testing of bearing boxes, in which a turn-table is provided with a basin in which the bearing box is immersed.
A number of piezoelectric transducers, which sweep the inner surface of the bearing box during its rotation, are centrally and vertically disposed one under another.
The piezoelectric transducers are connected with a fault detector having a monitor and a recorder. In case a linkage or porosity fault appears at the metal walls of the bearing box, the monitor becomes effected to transmit on electric signal to the recorder, which marks the fault on paper in spot form.
That apparatus has the disadvantage that the bearing boxes to be tested are checked only over an angle of 180.degree. and, in order to locate the fault, one must know the starting point, and then one must transpose the recording onto the actual scale of the bearing box. Furthermore, it does not allow the testing of different types of bearing boxes (regarding their diameters and heights) and poses problems for the very high bearing boxes, requiring a large number of sensors.
Another ultrasonic automatic test apparatus, for tube welds provides a distinct simultaneous recording of the fault on a drum, using a vertical rod provided with a radial arm on which a feeler is mounted, the rod moving in a fixed nut, thus creating a helical control movement at the level of the welded area.
That apparatus has the disadvantage that it requires contacts between the feeler and the fault detector in order to permit the helical movement of the feeler, thereby introducing contact error.
A device is also known for determining ultrasonically faults on long metal bodies, such as welding areas, the part to be tested rotating continuously, step by step, around its own axis, passing through an electrolyte recipient in which the supersonic echo sounder is immersed. Near the supersonic echo sounder there is a fixed electrode, the fault signal received from the ultrasonic apparatus produces an electric field between the electrode and the surface of the part, the fault area being marked by an electroplating on the surface of the part to be tested.
That device has the disadvantage of the long time required by electroplating and by the moving of the welded part to be tested.